L-Tetrahydrodipicolinic acid 1, a key intermediate of diaminopimelate metabolism has been prepared in 6 steps and 23% overall yield from L-allylglycine 4. The key step during this synthesis involves a base mediated cyclisation of dimethyl (2RS,6S)-2-[N-(benzyloxycarbonyl)-N-(p-tolylsulfonyl)amino]-6-[N-(benzyloxycarbonyl)amino]heptane-1,7-dioate 8 to give (2S)-N-(benzyloxycarbonyl)-1,2,3,4-tetrahydropyridine-2,6-dicarboxylic acid 9. 1H NMR studies show this one pot transformation involves four steps; base elimination of toluene-p-sulfinic acid, intramolecular nucleophilic attack of the 6-benzyloxycarbonylamino group on the resulting imine, followed by hydrolysis of the esters and elimination
of benzyl carbamate under acidic work-up to give the cyclic enamine 9.
L-四氢二
吡啶羧酸1是二
氨基
庚二酸代谢的关键中间体,已通过6步反应从L-烯丙基甘
氨酸4以23%的总产率制备得到。该合成过程中的关键步骤涉及二甲基(2RS,6S)-2-[N-(苄氧羰基)-N-(对
甲苯磺酰)
氨基]-6-[N-(苄氧羰基)
氨基]
庚烷-1,7-二酸酯8的碱介导环化反应,生成(2S)-N-(苄氧羰基)-
1,2,3,4-四氢吡啶-2,6-二
羧酸9。1H NMR研究表明,这一步反应涉及四个步骤:
对甲苯磺酸的碱消除反应、6-苄氧羰
氨基团对新生成的
亚胺的分子内亲核攻击、随后酯的
水解以及在酸性条件下苄氧羰胺的消除,最终得到环状烯胺9。